fetchExtendedChromInfoFromUCSC: Fetching chromosomes info for some of the UCSC genomes

Description Usage Arguments Details Value Note Author(s) See Also Examples

View source: R/fetchExtendedChromInfoFromUCSC.R

Description

Fetch the chromosomes info for some UCSC genomes. Only supports hg38, hg19, hg18, panTro4, panTro3, panTro2, bosTau8, bosTau7, bosTau6, canFam3, canFam2, canFam1, musFur1, mm10, mm9, mm8, susScr3, susScr2, rn6, rheMac3, rheMac2, galGal4, galGal3, gasAcu1, danRer7, apiMel2, dm6, dm3, ce10, ce6, ce4, ce2, sacCer3, and sacCer2 at the moment.

Usage

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fetchExtendedChromInfoFromUCSC(genome,
        goldenPath_url="http://hgdownload.cse.ucsc.edu/goldenPath",
        quiet=FALSE)

Arguments

genome

A single string specifying the UCSC genome e.g. "sacCer3".

goldenPath_url

A single string specifying the URL to the UCSC goldenPath location. This URL is used internally to build the full URL to the 'chromInfo' MySQL dump containing chromosomes information for genome. See Details section below.

quiet

TRUE or FALSE (the default). If TRUE then some warnings are suppressed. See below for the details.

Details

Chromosomes information (e.g. names and lengths) for any UCSC genome is stored in the UCSC database in the 'chromInfo' table, and is normally available as a MySQL dump at:

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  goldenPath_url/<genome>/database/chromInfo.txt.gz

fetchExtendedChromInfoFromUCSC downloads and imports that table into a data frame, keeps only the UCSC_seqlevel and UCSC_seqlength columns (after renaming them), and adds the circular logical column.

Then, if this UCSC genome is based on an NCBI assembly (e.g. hg38 is based on GRCh38), the NCBI seqlevels and GenBank accession numbers are extracted from the NCBI assembly report and the UCSC seqlevels matched to them (using some guided heuristic). Finally the NCBI seqlevels and GenBank accession numbers are added to the returned data frame.

Value

A data frame with 1 row per seqlevel in the UCSC genome, and at least 3 columns:

If the UCSC genome is *not* based on an NCBI assembly (e.g. gasAcu1, ce10, sacCer2), there are no additional columns and a warning is emitted (unless quiet is set to TRUE). In this case, the rows are sorted by UCSC seqlevel rank as determined by rankSeqlevels().

If the UCSC genome is based on an NCBI assembly (e.g. sacCer3), the returned data frame has 3 additional columns:

In this case, the rows are sorted first by level in the SequenceRole column, that is, assembled-molecules first, then alt-scaffolds, etc, and NAs last. Then within each group they are sorted by UCSC seqlevel rank as determined by rankSeqlevels().

Note

fetchExtendedChromInfoFromUCSC queries the UCSC Genome Browser as well as the FTP site at NCBI and thus requires internet access.

Only supports the hg38, hg19, hg18, panTro4, panTro3, panTro2, bosTau8, bosTau7, bosTau6, canFam3, canFam2, canFam1, musFur1, mm10, mm9, mm8, susScr3, susScr2, rn6, rheMac3, rheMac2, galGal4, galGal3, gasAcu1, danRer7, apiMel2, dm6, dm3, ce10, ce6, ce4, ce2, sacCer3, and sacCer2 genomes at the moment. More will come...

Author(s)

H. Pag<c3><a8>s

See Also

Examples

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## All the examples below require internet access!

## ---------------------------------------------------------------------
## A. BASIC EXAMPLE
## ---------------------------------------------------------------------

## The sacCer3 UCSC genome is based on an NCBI assembly (RefSeq Assembly
## ID is GCF_000146045.2):
sacCer3_chrominfo <- fetchExtendedChromInfoFromUCSC("sacCer3")
sacCer3_chrominfo

## But the sacCer2 UCSC genome is not:
sacCer2_chrominfo <- fetchExtendedChromInfoFromUCSC("sacCer2")
sacCer2_chrominfo

## ---------------------------------------------------------------------
## B. USING fetchExtendedChromInfoFromUCSC() TO PUT UCSC SEQLEVELS ON
##    THE GRCh38 GENOME
## ---------------------------------------------------------------------

## Load the BSgenome.Hsapiens.NCBI.GRCh38 package:
library(BSgenome)
genome <- getBSgenome("GRCh38")  # this loads the
                                 # BSgenome.Hsapiens.NCBI.GRCh38 package

## A quick look at the GRCh38 seqlevels:
length(seqlevels(genome))
head(seqlevels(genome), n=30)

## Fetch the extended chromosomes info for the hg38 genome:
hg38_chrominfo <- fetchExtendedChromInfoFromUCSC("hg38")
dim(hg38_chrominfo)
head(hg38_chrominfo, n=30)

## 2 sanity checks:
##   1. Check the NCBI seqlevels:
stopifnot(setequal(hg38_chrominfo$NCBI_seqlevel, seqlevels(genome)))
##   2. Check that the sequence lengths in 'hg38_chrominfo' (which are
##      coming from the same 'chromInfo' table as the UCSC seqlevels)
##      are the same as in 'genome':
stopifnot(
  identical(hg38_chrominfo$UCSC_seqlength,
            unname(seqlengths(genome)[hg38_chrominfo$NCBI_seqlevel]))
)

## Extract the hg38 seqlevels and put the GRCh38 seqlevels on it as
## the names:
hg38_seqlevels <- setNames(hg38_chrominfo$UCSC_seqlevel,
                           hg38_chrominfo$NCBI_seqlevel)

## Set the hg38 seqlevels on 'genome':
seqlevels(genome) <- hg38_seqlevels[seqlevels(genome)]
head(seqlevels(genome), n=30)

GenomeInfoDb documentation built on Oct. 6, 2017, 2:03 a.m.